This invention relates to repair of articles, and more particularly to repair of gas turbine engine components manufactured from certain iron-nickel base and nickel-base alloys.
A number of components of gas turbine engines are subject to high temperature environments during engine operation, and are also required to maintain minimum strength properties during engine operation. Such components are often fabricated of relatively expensive metal alloys which have been developed to withstand high temperature environments while maintaining required strength properties. Accordingly, if the component is damaged, either during manufacturing or due to service conditions, it is desirable to repair the component if at all possible, so as to avoid the expense of a new component.
One repair procedure which can be used for repairing damaged components involves welding, such as to repair a cracked component. Welding, however, can affect the metallurgical properties of the base material from which the component is manufactured. Post weld heat treatments can be used to at least partially restore desirable metallurgical characteristics of the base material close to the weld.
Still, it can be difficult to weld repair components manufactured from certain iron-nickel base and nickel base alloys. In particular, repair of components manufactured from certain iron-nickel base alloys can be difficult to weld repair due to lack of a suitable post weld heat treatment.
The present invention, in one form, provides a method for heat treating a weld repaired article formed of an iron-nickel base alloy. The component can be a new, unused part cracked or otherwise damaged in the manufacturing process, or a used part cracked or otherwise damaged after service. The method is believed to be especially useful in weld repair of gas turbine engine components formed of INCOLOY 909, though it may also be useful in the repair of other iron-nickel and nickel base alloys, such as RENE 41, INCOLOY 903, INCOLOY 907, AND INCONEL 718.
The method, in one form, includes heat treating a component formed of an iron-nickel base alloy having one or weld repaired portions. The steps of heat treating can include heating the repaired portion to a first hold temperature of at least about 1775 degrees Fahrenheit; cooling the repaired portion to about 1025 degrees Fahrenheit or less; heating the repaired portion, at a rate of at least about 10 degrees Fahrenheit per minute or greater, to a second hold temperature of at least about 1525 degrees Fahrenheit; cooling the repaired portion to a third hold temperature of about 1425 degrees Fahrenheit or less; and cooling the repaired portion to a fourth hold temperature of about 1225 degrees Fahrenheit or less.
The method, in one embodiment, includes the steps of providing a component formed of INCOLOY 909, identifying one or more cracks in the component, weld repairing the cracks, and post weld heat treating the component. The step of heat treating can include heating the repaired portion to a first hold temperature of between about 1775 and about 1825 degrees Fahrenheit and holding the component at the first hold temperature for between about 50 to about 70 minutes; furnace cooling the component to between about 975 and about 1025 degrees Fahrenheit; heating the component at a rate of at least about 10 degrees Fahrenheit per minute to a second hold temperature of between about 1525 and about 1575 degrees Fahrenheit and holding the component at the second hold temperature for between about 50 and about 70 minutes; furnace cooling the component to a third hold temperature of between about 1375 and about 1425 degrees Fahrenheit and holding the component at the third hold temperature for between about 4 hours and 40 minutes to about 5 hours and 20 minutes; furnace cooling the component to a fourth hold temperature between about 1175 and about 1225 degrees Fahrenheit and holding the component at the forth hold temperature for between about 50 to about 70 minutes; and cooling the component to about 500 degrees Fahrenheit.